Cutting device

ABSTRACT

A cutting device includes a cutter rod, and a movable cutting tool of a length greater than the diameter of the cutter rod. The movable cutting tool is prevented from cracking and breaking.  
     A movable cutting tool ( 7 ) has protruding parts ( 7   b ) protruding radially outward from a large-diameter part ( 40   b ) of a cutter rod ( 4 ) and having cylindrical surfaces ( 7   c ) of a cylinder of a radius equal to that of the large-diameter part ( 40   b ). The movable cutting tool ( 7 ) is attached to a flat surface ( 40   c ) formed in the cutter rod ( 4 ) with the cylindrical surfaces ( 7   c ) in close contact with the circumference of the large-diameter part ( 40   b ) of the cutter rod ( 4 ) to bear external force exerted on the protruding parts ( 7   b ) by the cutter rod ( 4 ).

TECHNICAL FIELD

The present invention relates to a cutting device for cutting a metalplate or a metal round bar. More particularly, the present inventionrelates to a cutting device characterized by a movable cutting toolholding structure.

BACKGROUND ART

A cutting device that cuts a metal workpiece by sliding a movablecutting tool attached to a free end of a reciprocating rod relative to afixed cutting tool is used widely.

FIG. 6 shows a conventional cutting device 60 by way of example in asectional view. The cutting device 60 has a base 61, a fixed cuttingtool 62 having the shape of a flat plate and fixedly held on the base61, and a movable cutting tool 64 having the shape of a flat plate andattached to a front part of a reciprocating cutter rod 63 thatreciprocates relative to the fixed cutting tool 62. The movable cuttingtool 64 is slidably moved to cut a workpiece, such as a metal round barP.

This cutting device 60 is capable of cutting not only round bars butalso metal plates having a comparatively large width. The movablecutting tool 64 has a cutting edge 64 a of a length greater than thediameter of the cutter rod 63.

The cutting tool 64 is applied to a longitudinal flat surface formed bylongitudinally cutting a part of the front part of the cutter rod 63,and is fastened to the cutter rod 63 with bolts 65.

The cutter rod 63 is advanced by the agency of a high-pressure oilsupplied through a high-pressure pipe 66 to cut the round bar P bysliding the movable cutting tool 64 relative to the fixed cutting tool62.

DISCLOSURE OF THE INVENTION

However, when cutting the round bar P by the cutting device with only aprotruding part 64 b, protruding radially outward from the cutter rod63, of the movable cutting tool 64 having the cutting edge 64 a as shownin FIG. 6, a large bending moment acts on the protruding part 64 b ofthe movable cutting tool 64. Consequently, in some cases, the movablecutting tool 64 cracks and breaks at a part corresponding to the jointof the protruding part 64 b and the cutter rod 63.

The present invention has been made to solve such a problem and it istherefore an object of the present invention to provide a cutting devicehaving a cutter rod and a flat cutting tool having a cutting edge and alength greater than the diameter of the cutter rod, and capable ofpreventing the cracking fracture of the movable cutting tool.

To solve the foregoing problem, the present invention provides a cuttingdevice including: a fixed cutting tool; a reciprocating, cylindricalcutter rod having a front part having a flat surface and capable ofbeing axially moved; a flat movable cutting tool having a cutting edgeof a length greater than the diameter of the cutter rod and attached tothe flat surface of the front part of the cutter rod; characterized inthat the front part of the cutter rod has a small-diameter part of asmall diameter and a large-diameter part of a large diameter, the flatsurface is formed in the small-diameter part, cylindrical surfaces of acylinder of a radius equal to that of the large-diameter part of thecutter rod are formed in protruding parts, protruding radially outwardfrom the large-diameter part of the cutter rod, of the movable cuttingtool, respectively, and the movable cutting tool is attached to the flatsurface of the cutter rod with the cylindrical surfaces in close contactwith the circumference of the cutter rod.

The cutting device of the present invention is characterized by the pairof cylindrical surfaces, and the movable cutting tool is attached to thecutter rod with its middle part in coincidence with the axis of thecutter rod.

According to the present invention, external forces acting on theprotruding parts of the movable cutting tool extending radially outsidethe cutter rod are borne by the circumference of the cutter rod toprevent the cracking breakage of the protruding parts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a cutting device in a preferred embodimentaccording to the present invention;

FIG. 2 is a top plan view of the cutting device shown in FIG. 1;

FIG. 3 is a side elevation of a front part of a cutter rod;

FIG. 4 is a perspective view of a movable cutting tool;

FIG. 5 is a perspective view of a movable cutting tool attached to afront part of a cutter rod; and

FIG. 6 is a sectional view of a conventional cutting device.

BEST MODE FOR CARRYING OUT THE INVENTION

A cutting device 10 in a preferred embodiment according to the presentinvention will be described in connection with the accompanyingdrawings.

FIG. 1 is a sectional view of the cutting device 10 embodying thepresent invention, and FIG. 2 is a top plan view of the cutting device10 shown in FIG. 1.

Referring to FIGS. 1 and 2, a flat fixed cutting tool 2 is fixedlyattached to a front part of a base 1.

A cylinder 3 is formed in a back part of the base 1. A cutter rod 4 isinserted in the cylinder 3 so as to be axially movable. The cutter rod 4is advanced by high-pressure oil supplied through a high-pressure pipeinto the cylinder 3 and is retracted by a return spring 6 disposed inthe cylinder 3.

Referring to FIG. 3, a front part 40 of the cutter rod 4 projecting fromthe cylinder 3 has a small-diameter part 40 a and a large-diameter part40 b. A part of the small-diameter part 40 a is cut off axially to forma flat surface 40 c. Through holes 40 d to be used for attaching themovable cutting tool 7 to the cutter rod 4 are formed in the flatsurface 40 c. A flat end surface 40 e is formed between thesmall-diameter part 40 a and the large-diameter part 40 b.

Referring to FIG. 4 showing the movable cutting tool 7 in a perspectiveview, the movable cutting tool 7 is formed in the shape of a flat plateand has a cutting edge 7 a. The length of the cutting edge 7 a isgreater than the diameter of the large-diameter part 40 b. The movablecutting tool 7 has protruding parts 7 b protruding radially outward fromthe cutter rod 4. Cylindrical surfaces 7 c of a cylinder of a radiusequal to that of the large-diameter part 40 a are formed in back endparts of the protruding parts 7 b, respectively.

The cylindrical surfaces 7 c are formed in a shape and dimensions suchthat the cylindrical surfaces 7 c are in close contact with thecircumference of the large-diameter part 40 b of the cutter rod 4 whenthe movable cutting tool 7 is attached to the flat surface 40 c of thecutter rod 4.

In this embodiment, the paired cylindrical surfaces are formed on theopposite sides, respectively, of the middle part of the cutting edge 7a.

Threaded holes 7 d are formed in a flat part of the movable cutting tool7 so as to coincide with the through holes 40 d formed in thesmall-diameter part 40 c of the cutter rod 4, respectively. A verticalsurface 7 e extends between the paired cylindrical surfaces 7 c.

FIG. 5 is a perspective view of the movable cutting tool 7 attached tothe cutter rod 4.

Bolts 8 passed through the through holes of the small-diameter part 40 aare screwed in the threaded holes 7 d to fasten the movable cutting tool7 to the front part 40 of the cutter rod 4. In this state, thecylindrical surfaces 7 c of the protruding parts 7 b protruding radiallyoutward from the large-diameter part 40 a are in close contact with thecircumference of the large-diameter part 40 b, and the vertical surface7 e of the movable cutting tool 7 is in close contact with the flat endsurface 40 e of the front part 40 of the cutter rod 4.

The cutter rod 4 of the cutting device 10 embodying the presentinvention thus constructed is advanced by supplying the high-pressureoil through the high-pressure pipe 5 into the cylinder 3. Consequently,the movable cutting tool 7 slides relative to the fixed cutting tool 2to cut a metal plate B or a metal round bar P.

When, for example, the protruding part 7 b is used for cutting a roundbar P as shown in FIG. 1, a large bending moment acts on the protrudingpart 7 b. Since the cylindrical surface 7 c of the protruding part 7 bis in close contact with the circumference of the large-diameter part 40b of the cutter rod 4, this bending moment is borne by thelarge-diameter part 40 b of the cutter rod 4. Consequently, theload-bearing ability of the protruding part 7 b is enhanced to preventthe cracking breakage of the protruding part 7 b. The vertical surface 7e in close contact with the flat end surface 40 e further enhances theload-bearing ability.

In this embodiment, the movable cutting tool 7 is attached to the cutterrod 4 such that the middle part of the cutting edge 7 a coincides withthe axis of the cutter rod 4, and the two protruding parts 7 b protruderadially outward from the cutter rod 4. The movable cutting tool 7 mayhave a single protruding part.

As apparent from the foregoing description, according to the presentinvention, the movable cutting tool has the protruding parts protrudingradially outward from the large-diameter part of the cutter rod andrespectively having the cylindrical surfaces, and the movable cuttingtool is attached to the flat surface of the cutter rod with thecylindrical surfaces of the protruding parts in close contact with thecircumference of the large-diameter part of the cutter rod. Therefore,high external force exerted on the protruding parts can besatisfactorily borne by the cutting rod and thereby the protruding partsare prevented from cracking and breaking.

The present invention is particularly effective for and applicable to acutting device for cutting comparatively wide flat members and roundbars, such as an emergency rescue device for cutting the brake pedal orthe accelerator pedal of an automobile when the driver's foot is caughtin the brake pedal or the accelerator pedal during an auto accident.

1. A cutting device comprising: a fixed cutting tool; a reciprocating,cylindrical cutter rod having a front part having a flat surface andcapable of being axially moved; and a flat movable cutting tool having acutting edge of a length greater than the diameter of the cutter rod andattached to the flat surface of the front part of the cutter rod;characterized in that the front part of the cutter rod has asmall-diameter part of a small diameter and a large-diameter part of alarge diameter, the flat surface is formed in the small-diameter part,cylindrical surfaces of a cylinder of a radius equal to that of thelarge-diameter part of the cutter rod are formed in protruding parts,protruding radially outward from the large-diameter part of the cutterrod, of the movable cutting tool, respectively, and the movable cuttingtool is attached to the flat surface of the cutter rod with thecylindrical surfaces in close contact with the circumference of thecutter rod.
 2. The cutting device according to claim 1 characterized inthat the pair of cylindrical surfaces are formed in the movable cuttingtool, and the movable cutting tool is attached to the cutter rod withits middle part in coincidence with the axis of the cutter rod.